Hydraulically Amplified Terfenol-D Actuator for Adaptive Powertrain Mounts

Abstract

A magnetostrictive actuator with a stroke of ±1 mm and a blocked force of ±25 N has been developed based on a Terfenol-D driver and a hydraulic stroke amplification mechanism. A mechanical model for this magneto-hydraulic actuator (MHA) is formulated by combining linear piezomagnetic relations for Terfenol-D and a lumped parameter mechanical system model describing the system vibrations. Friction at the fluid seals is described by the LuGre model. The model accurately describes the frequency-domain behavior of the actuator in mechanically-blocked and mechanically-free conditions. The MHA is benchmarked against a commercial electromagnetic driver used in active powertrain mounts in terms of mechanical performance (blocked force and unloaded displacement) and electrical power consumption. Measurements show that the MHA achieves more than twice the frequency bandwidth of the commercial device in the free displacement response, along with comparable static displacements. The commercial device produces higher blocked forces in the frequency range of 10 Hz to 120 Hz beyond which the generated forces are comparable up to 400 Hz. Spectral analysis reveals significant second order components in the commercial actuator displacement response which are absent in the MHA. Further, the MHA achieves superior performance than the commercial actuator operated at maximum current (6 A) with power consumption identical to that of the commercial actuator operated at minimum current (4 A).